1. Field of the Invention
The present invention relates to a laminate cell having a structure, in which a metal composite film is used for a cell package hermetically sealing a power generating element and an electrolyte, and in which positive and negative tabs are drawn from the end edges of this cell package to the outside. The present invention also relates to an assembled battery, a battery module, and an electric vehicle, all of which use this laminate cell.
2. Description of the Related Art
In recent years, an electric vehicle which uses electricity as a power source and a hybrid car which runs by a combination of an engine and a motor have attracted attention due to the global problem of environmental air pollution caused by automobile exhaust gas. Thus, the development of a high-power battery to be mounted in these types of vehicles, which achieves high energy/power densities, occupies an important position in the industry.
Regarding this type of high-power battery, for example, there is a lithium ion battery. Specifically, among this type of battery, there is a laminate cell formed by stacking flat positive and negative electrode plates upon one another while interposing separators therebetween.
As for this laminate cell, one disclosed in Japanese Patent Application Laid-Open No. 2000-200585 has been proposed, which uses, as a cell package, a laminate film formed by stacking a metal film and a polymer film. In this specification, the laminate film is referred to as a metal composite film. This laminate cell is constructed in a such manner that a power generating element composed of positive and negative electrode plates and separators, all of which have an approximately rectangular flat shape, are hermetically sealed together with an electrolyte by the cell package made of the metal composite film, and a positive tab connected to the positive electrode plates of the power generating element and a negative tab connected to the negative electrode plates thereof are drawn outward from the end edges of the cell package.
The laminate cell thus constructed has an advantage in that it is easier to reduce the weight and thickness thereof in comparison with one which uses a metal can as the cell package.
Incidentally, in the laminate cell thus constructed, it is common that, the positive tab connected to the positive electrode plates of the power generating element and the negative tab connected to the negative electrode plates thereof are drawn outward from the end edges of the short sides of the cell package made of the metal composite film from the viewpoint of securing the sealing capability, and the like.